Power Inverter for S8 Auto

[karessamom]

is it required that you must have a pure sine wave power inverter to operate the resmed S8 or would the modified sine wave power inverters work?
Reason--we are going camping this weekend and we can find a regular inverter that would work for about $40 but to get the pure sinewave it's going to be over $100. I didn't know there were 2 different kinds and was thinking the other would work. My husband's Auto also has a DC port but we would need a special plug for that too wouldn't we??

[jdm2857]

The S8 AutoSet II has a 12V DC input jack just above where the power cord attaches. It will run on any 12V DC source with enough capacity without an inverter. ResMed recommends using their DC to DC unit to protect the APAP from a drained battery or reversed polarity, but it is not essential. If you don't use the ResMed converter, you will have to get a plug that mates with the unit and ensure that you use the correct polarity.

The humidifier will not run on DC. If you want to use it, you will have to run the unit on a pure sine wave inverter. Square wave and modified sine wave inverters will damage the humidifier.

[TheOneBlackMage]

Here is ResMed's PDF on battery requirements:

http://www.resmed.com/us/documents/batt ... ts-usa.pdf

I have an S8 Elite II and the requirements are pretty similar to the Auto.

You can use a converter which runs off pure DC (12V) and plugs into a battery. The standard ResMed converter has the "cigarette lighter" plug. The details and a picture of the converter are on page 6.

The S8 Auto without humidifer can run on a 150-Watt modified or pure sine wave inverter. If you want to run with the humidifier, you're going to need a much larger battery, and it will require a 200-Watt pure sine wave inverter. -edit- The PDF indicates you cannot use a heated humidifer (i.e. 4i) with an inverter.

The power efficiency difference for inverter vs converter is a lot less than it used to be. You can see the differences in the battery requirements for the two options in that PDF, and it isn't a large difference.

Just for research, here are two options for the S8 series:

S8 Pure Sine Wave Inverter:
https://www.cpap.com/productpage/DC-to- ... or-s8.html
-edit- This isn't a ResMed product

S8 DC 12V Converter Cable:
https://www.cpap.com/productpage/DC-12-Inverter.html
-edit- This is the official ResMed 12V DC cable

[karessamom]

Thank you so much for your comments. They helped alot

[tattooyu]

That definitely helps A LOT! I was still confused about the different setups until I read this post.

Just so I am clear on the inverter setup:

Marine or Deep Cycle battery ► Inverter ► S8 Autoset II (no humidifer)

Since I have an S8 Autoset II with the H4i heated humidifer, I wonder if I could keep it hooked up and just run it in passive mode without damaging anything?

[TheOneBlackMage]

That definitely helps A LOT! I was still confused about the different setups until I read this post.

Just so I am clear on the inverter setup:

Marine or Deep Cycle battery ► Inverter ► S8 Autoset II (no humidifer)

Since I have an S8 Autoset II with the H4i heated humidifer, I wonder if I could keep it hooked up and just run it in passive mode without damaging anything?

Yes - Battery to Inverter will convert the DC to AC, then you plug in your S8 using the regular AC plug.

I think running the H4i in passover mode (without turning on the heat element) should be fine with the 200W pure sine inverter. There's no extra power being used if the element stays off- the blower just has to work a bit harder to maintain the pressure from the extra area inside the water reservoir. To be sure, you could contact ResMed to confirm though. Let us know what they say

[tattooyu]

I just spoke with "Bud" (could have been "Bub") at ResMed technical support. Really nice guy.

He said that the brochure which states that you cannot use a heated humidifier is a little misleading. If you have a Pure Sine Wave inverter that can output 300 watts or more, you can use the heated humidifier, but it will take up more juice.

My pressure is just under 14 cm. I sleep 7 hours per night on average.

Without a humidifier it takes 1.3 Ah (amp-hours) of power.

With a heated humidifier it takes 3.8 Ah of power.

So, if I wanted 4 nights with my CPAP (w/ heated humidifer), I believe I would need a 110 Ah deep cycle/marine battery. With that same battery, I could get somewhere around 9 nights of sleep with my CPAP (humidifier in passover mode).

[billbolton]

is it required that you must have a pure sine wave power inverter to operate the resmed S8 or would the modified sine wave power inverters work?

The Resmed S7 and S8 flow generators will run fine on modified sine wave AC, however, the Resmed humidifiers require pure sine wave AC power.

Cheers,

Bill

[jdm2857]

The S8s (I don't know about the S7s) will run on a 12 V battery WITHOUT AN INVERTER if you do not use the humidifier. I would remove the humidifier to be safe.

The humidifier only runs on clean AC -- either from the power company, a generator, or a battery and a pure sine wave inverter.

[tattooyu]

The S8s (I don't know about the S7s) will run on a 12 V battery WITHOUT AN INVERTER if you do not use the humidifier. I would remove the humidifier to be safe.

The humidifier only runs on clean AC -- either from the power company, a generator, or a battery and a pure sine wave inverter.

Jdm, if I was going to use it without the humidifier, would I use it as the following?

Deep Cycle Battery ► DC-12 Convertor ► S8 Autoset II

Just to confirm, you would recommend not using the humidifier even in passover mode with this setup?

[jdm2857]

That setup is what ResMed recommends. The converter is added protection for your machine. If you know what you are doing, and can find the polarity of the machine's connection, you should be able to make your own connector with Radio Shack and auto store parts.

The problem with the humidifier is that as I understand it, the H4i can be damaged if run on DC. While it should be safe when off, I would at least tape the dial in the off position so that no damage to the humidifier occurs.

[tattooyu]

Thanks.

[Piefke]

Bill, I have seen you a few times on this forum and you look like you REALLY know what you are talking about on those S8's.
Here comes:
I have an autoscore II S8 for which I had a battery pack made (reversible polarity because I have a Good Knight and an S8 who use different polarities, I have learned).
I understand the polarity in these S8's IS OF NO CONSEQUENCE on DC power (read it somewhere, not sure where). They simply don't work if polarity is wrong but they don't burn the little fuse inside.
My machine gave a little light recently before remaining silent for good, when I connected my battery on a plane to Brazil.
Since then, nothing work, DC, AC all dead.
Took machine apart because I was in Brazil and needed to sleep. Could not get fitting fuse, Sunday etc., so ended up buying a new machine in Brazil. Not the end of the world, always good to have a backup.
Now, Mr. Resmed suggests I send him the machine, open as it is (very much frowned upon, even in such real life out of the ordinary situation as explained in detail) and fork out north of 400 $ to get a new circuit board for the power only (not main board).
Well, I am not too keen on doing that!
Question to you:
1. Polarity an issue on S8 or is it correct that no damage is done with wrong polarity?
2. either way, other than the small F1 (2 A, 250 V) fuse, is there another one?
3. ANY IDEAS?

I am with my new machine now and really want this old to be good back-up, not useless paper-weight.

You help is highly appreciated.

Regards
Michael

is it required that you must have a pure sine wave power inverter to operate the resmed S8 or would the modified sine wave power inverters work?

The Resmed S7 and S8 flow generators will run fine on modified sine wave AC, however, the Resmed humidifiers require pure sine wave AC power.

Cheers,

Bill

[billbolton]

Question to you:
1. Polarity an issue on S8 or is it correct that no damage is done with wrong polarity?

Its correct that you WILL instantly damage an S8 if you connect the wrong DC polarity to it.

2. either way, other than the small F1 (2 A, 250 V) fuse, is there another one?

Sorry, I have no idea.

I suspect, from the instantaneous nature of the failure, that a semiconductor PN junction in an active device in the DC power regulator is blown when reverse polarity is applied - but that's just my theory.

3. ANY IDEAS?

Its just not intended for field servicing

Cheers,

Bill

[Piefke]

thanks for your quick reply.
I appreciate the clarity of it too, but must find again where I got the wisdom from that reversed polarity in an S8 does NOT damage but only results in non function. Again, thanks. Will report once fault repaired - and what actually blew.
Cheers
Michael